Transmission and method for controlling a transmission for a motor vehicle

ABSTRACT

A transmission, in particular an automated shift transmission, includes a plurality of selectable and deselectable gear stages for implementing gear changes. The selection and deselection of the gear stages is achieved with the aid of coupling units, in particular with the aid of engageable and disengageable sliding collars. The coupling units are activatable via respective shift rails and respective actuators. The shifting times are reduced and a compact construction of the transmission is achieved by virtue of the fact that a plurality of gear stages is assigned to at least two different shift rails in such a way that respective successive gear stages are assigned to respective different shift rails. As a result, the respective shift rails can be activated at least partially simultaneously in the case of a sequential gear change. A method for controlling a transmission is also provided.

CROSS REFERENCE TO RELATED APPLICATION

[0001] This is a divisional of U.S. application Ser. No. 10/241,553,filed Sep. 11, 2002. This application also claims the benefit of Germanapplication No. 101 45 918.1, filed Sep. 18, 2001, under 35 U.S.C.Section 119. Both applications are herewith incorporated by reference.

BACKGROUND OF THE INVENTION FIELD OF THE INVENTION

[0002] The invention relates to a transmission for a motor vehicle, inparticular an automated shift transmission, with a plurality ofselectable and deselectable gear stages for implementing gear changes.The selection and deselection of the gear stages can be achieved bycoupling units, in particular by engageable and disengageable slidingcollars. The coupling units can be activated by shift rails and byrespective actuators provided for this purpose, wherein particular gearstages are assigned to particular shift rails. The invention furthermorerelates to a method for controlling a transmission. A plurality of gearstages can be selected and/or deselected in the transmission in order toimplement gear changes. The selection and deselection of the gear stagesis achieved with the aid of coupling units, in particular with the aidof engageable and disengageable sliding collars. The coupling units areactivated by shift rails and by respective actuators provided for thispurpose, wherein particular gear stages are assigned to particular shiftrails.

[0003] Transmissions and methods for controlling transmissions for motorvehicles, wherein the transmissions have a given number of shift rails,are known. In these conventional transmissions, the shift rails arearranged such that they are effective, in terms of their operation,between the respective coupling units and the respective actuators. Inother words, a coupling unit, which is preferably embodied as anengageable and disengageable sliding collar and with the aid of whichthe respective gear stage can be selected or deselected within thetransmission, is actuated, via the shift rail, with the aid of therespective actuator, wherein the shift rail is arranged to be moveablewithin the transmission. As a result, the respective gear stage iseither selected or deselected. In the conventional transmissions,specific gear stages are assigned to specifically corresponding shiftrails. In this case, the first and the second gear stage are assigned toa first shift rail, the third and the fourth gear stage are assigned toa second shift rail and the fifth and the six gear stage are assigned toa third shift rail. In other words, the respective sequential gearchanges between the first and second, the third and fourth gear etc. canbe implemented with the aid of the first, second and third shift railrespectively by in each case correspondingly activating or moving justone shift rail.

[0004] Published, Non-Prosecuted German Patent Application No. DE 199 12817 A1 discloses a device and a method in which a plurality of couplingunits are provided within the transmission in order to reduce shiftingtimes during gear changes, wherein the coupling units are separated fromone another. In other words, the separate coupling units provided withinthe transmission, which can each be activated individually by separateactuators, preferably by Bowden cables, implement the individual gearchanges within the transmission in a relatively short time since, in thecase of sequential gear changes for example, when changing from first tosecond gear for example, two actuators and two coupling units are ineach case activated simultaneously in order to implement thecorresponding gear change. As a result, the shifting times here arecorrespondingly reduced.

[0005] In the case of the conventional devices and methods, i.e. in thecase of the conventional transmissions, their control equipment is verycomplex and is therefore not only fault-prone but requires acorrespondingly large amount of space when constructing the transmissionin order to be able to implement the latter in an appropriate manner.Either, the control equipment for reducing the shifting times inconventional transmissions is very expensive and also fault-prone, suchthat it is impossible in this case to construct the transmissions in acompact way, or, the conventional transmissions can be constructed in acompact way and without complex control equipment but then haverelatively long shifting times in the case of a gear change involvinggear stages that are provided sequentially one after another.

SUMMARY OF THE INVENTION

[0006] It is accordingly an object of the invention to provide atransmission which overcomes the above-mentioned disadvantages of theheretofore-known transmissions of this general type and which reducesthe shifting times for a gear change without the need for costly,fault-prone control equipment and which, at the same time, allows acompact construction of the transmission.

[0007] With the foregoing and other objects in view there is provided,in accordance with the invention, a transmission for a motor vehicle,including:

[0008] shift rails;

[0009] gear stages assigned to the shift rails such that respectivesuccessive ones of the gear stages are assigned to respective differentones of the shift rails;

[0010] the shift rails being configured such that, in a sequential gearchange, respective ones of the shift rails are activated at leastpartially simultaneously;

[0011] coupling units operatively connected to respective ones of theshift rails and configured to select and deselect the gear stages forperforming gear changes;

[0012] actuators operatively connected to respective ones of the shiftrails; and

[0013] the coupling units being configured to be activated viarespective ones of the shift rails and respective ones of the actuators.

[0014] In other words, the object of the invention is achieved, by atransmission for a motor vehicle, in particular an automated shifttransmission, with a plurality of selectable and deselectable gearstages for implementing gear changes, the selection and deselection ofthe gear stages being achievable with the aid of coupling units, inparticular with the aid of engageable and disengageable sliding collars,the coupling units being activatable by shift rails and by respectiveactuators, and particular gear stages being assigned to particular shiftrails, wherein a plurality of gear stages is assigned to at least twodifferent shift rails in such a way that the respective successive gearstages are assigned to different shift rails, with the result that therespective shift rails can be activated at least partiallysimultaneously in the case of a sequential gear change.

[0015] According to another feature of the invention, a first one of theshift rails has a first and a third one of the gear stages assignedthereto; and the first one of the shift rails is activated by a firstone of the actuators.

[0016] According to yet another feature of the invention, a second oneof the shift rails has a second and a fourth one of the gear stagesassigned thereto; and the second one of the shift rails is activated bya second one of the actuators.

[0017] According to a further feature of the invention, a third one ofthe shift rails has a fifth one of the gear stages assigned thereto; andthe third one of the shift rails is activated by a third one of theactuators.

[0018] According to yet a further feature of the invention, the thirdone of the shift rails further has a seventh one of the gear stagesassigned thereto; and a fourth one of the shift rails has a sixth and aneighth one of the gear stages assigned thereto.

[0019] According to another feature of the invention, the shift rails,the coupling units and the actuators form a motor vehicle transmissionconfiguration.

[0020] According to yet another feature of the invention, the shiftrails, the coupling units and the actuators form an automated shifttransmission configuration.

[0021] According to another feature of the invention, the coupling unitsare sliding collars configured to be engageable and disengageable.

[0022] With the objects of the invention in view there is furtherprovided, a transmission configuration, including:

[0023] a first shift rail and a second shift rail;

[0024] a first gear stage, a second gear stage as a subsequent gearstage to the first gear stage, a third gear stage as a subsequent gearstage to the second gear stage, and a fourth gear stage as a subsequentgear stage to the third gear stage;

[0025] the first shift rail controlling the first gear stage and thethird gear stage;

[0026] the second shift rail controlling the second gear stage and thefourth gear stage; and

[0027] the first shift rail and the second shift rail beingsimultaneously activated in case of a sequential gear change.

[0028] With the objects of the invention in view there is also provided,a method for controlling a transmission for a motor vehicle, the methodincludes the steps of:

[0029] providing gear stages assigned to at least two shift rails suchthat respective successive ones of the gear stages are assigned torespective different ones of the shift rails; and

[0030] performing gear changes by using coupling units activated viarespective shift rails and respective actuators for selecting anddeselecting the gear stages in the transmission and, in case ofperforming a sequential gear change, activating respective ones of theshift rails at least partially simultaneously in order to perform thesequential gear change.

[0031] In other words, the abovementioned object is achieved by a methodfor controlling a transmission for a motor vehicle, in particular atransmission as defined above, wherein a plurality of gear stages areselected and/or deselected in the transmission to implement gearchanges, the selection and deselection of the gear stages being achievedwith the aid of coupling units, in particular with the aid of engageableand disengageable sliding collars, the coupling units being activated byshift rails and by respective actuators, and particular gear stagesbeing assigned to particular shift rails, wherein a plurality of gearstages is assigned to at least two different shift rails in such a waythat the respective successive gear stages are assigned to differentshift rails, with the result that the respective shift rails areactivated at least partially simultaneously in the case of a sequentialgear change.

[0032] Another mode of the method according to the invention includesthe steps of activating a first shift rail by using a first actuator;and respectively selecting and deselecting a first gear stage and athird gear stage by using the first shift rail.

[0033] Yet another mode of the method according to the inventionincludes the steps of activating a second shift rail by using a secondactuator; and respectively selecting and deselecting a second gear stageand a fourth gear stage by using the second shift rail.

[0034] Another mode of the method according to the invention includesthe steps of activating a third shift rail by using a third actuator;and respectively selecting and deselecting a fifth gear stage and aseventh gear stage by using the third shift rail.

[0035] A further mode of the method according to the invention includesthe steps of activating a fourth shift rail by using a fourth actuator;and respectively selecting and deselecting a sixth gear stage and aneighth gear stage by using the fourth shift rail.

[0036] Another mode of the method according to the invention includesthe step of providing the coupling units as selectively engageable anddisengageable sliding collars.

[0037] The invention is based fundamentally on the principle that, in atransmission with correspondingly provided shift rails, the respectivegear stages are assigned to the various particular shift rails in aparticular manner, namely in such a way that the gear stages that followone another sequentially are provided on various, namely different,shift rails. This allows a partly simultaneous activation of thedifferent shift rails on which the successive gear stages are providedand, due to the partially simultaneous activation of these differentshift rails, the corresponding shifting time for the implementation ofthe gear change can be kept correspondingly short. As an advantageousresult, short shifting times can thereby be achieved. Further, thenumber of shift rails in the transmission does not have to be increasedand the control equipment does not have to be enhanced, in other wordsconstructional outlay and corresponding costs are not increased, therebyavoiding the disadvantages mentioned at the outset.

[0038] There are many ways of refining and developing the transmissionaccording to the invention and the method according to the invention inan advantageous manner.

[0039] Other features which are considered as characteristic for theinvention are set forth in the appended claims.

[0040] Although the invention is illustrated and described herein asembodied in a transmission and a method for controlling a transmissionfor a motor vehicle, it is nevertheless not intended to be limited tothe details shown, since various modifications and structural changesmay be made therein without departing from the spirit of the inventionand within the scope and range of equivalents of the claims.

[0041] The construction and method of operation of the invention,however, together with additional objects and advantages thereof will bebest understood from the following description of specific embodimentswhen read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0042]FIG. 1 is a schematic block diagram illustrating the shift railprinciple according to the prior art;

[0043]FIG. 2 is a diagram illustrating a shift sequence according to theprior art, in accordance with the shift rail principle illustrated inFIG. 1;

[0044]FIG. 3 is a schematic block diagram illustrating the shift railprinciple according to the invention; and

[0045]FIG. 4 is a diagram illustrating a shift sequence according to theinvention, in accordance with the shift rail principle illustrated inFIG. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0046] FIGS. 1 to 4 are schematic illustrations representing shiftsequences within a transmission for a motor vehicle. The transmissionhas shift rails or shift rods, which are arranged in such a way thatthey can be moved essentially within the transmission. Furthermore,coupling units, which are known per se, are provided within thetransmission in order to implement the corresponding gear changes. Thecoupling units are preferably embodied as engageable and disengageablesliding collars, which can be actuated with the aid of the shift rails.Each individual shift rail is activated by a corresponding actuator,i.e. the shift rail is moved or displaced appropriately. The actuatorsactivating the shift rails can be implemented in various ways.Electrically embodied actuators and/or hydraulically embodied actuatorscan be used. The type of actuator which is to be used is dependent onthe respective type of transmission and/or motor vehicle. Thetransmission is preferably embodied as an automated shift transmissionor auto-shift gearbox but other forms of transmission, in particularautomatic transmissions may also be used. The shift rail principleaccording to the invention, which is described here, is therefore notlimited to an automated shift transmission such as an automated manualshift transmission.

[0047] Also provided are components for implementing the control schemeor control system. In particular, the control system has a control unit,which is implemented as an electronic and/or electrical device.Particularly in an automatic shift transmission, the control unitdetermines the speed of the motor vehicle, engine control parameters andthe appropriate control parameters required to control the transmissionsequences, i.e. the gear changes to be implemented in the transmission,for example. Via control lines that are provided, the control unit thenactivates the corresponding individual actuators to implement the gearchanges or the selection and deselection of the respective gear stage.The basic principles of selecting or engaging a gear stage anddeselecting or disengaging a gear stage are in principle known andtherefore do not require any further detailed explanation.

[0048] The block diagram of FIG. 1 illustrates the conventional shiftrail principle according to the prior art. Five shift rails a, b, c, d,and e are schematically illustrated as rectangular boxes. Each of theshift rails a, b, c, d, and e illustrated here is assigned a respectiveactuator, through the use of which the respective shift rail a, b, c, d,and e can be activated or moved in an appropriate manner. Each shiftrail a, b, c, d, and e is furthermore operatively connected in anappropriate manner within the transmission to a corresponding couplingunit. The coupling unit is preferably an engageable and disengageablesliding collar which is only schematically illustrated in FIG. 1. Acrucial aspect is that, in the prior art, as illustrated by FIG. 1, thefirst gear stage 1 and the second gear stage 2 are assigned to the firstshift rail a, the third gear stage 3 and the fourth gear stage 4 areassigned to the second shift rail b, the fifth gear stage 5 is assignedto the third shift rail c, and the reverse gear R is also assigned tothe fifth shift rail e.

[0049] The shift sequence for the configuration or assignment of theshift rails and gear stages in accordance with FIG. 1, will be explainedin greater detail below with reference to FIG. 2 which shows in adiagrammatic manner a position s versus time t. In the case of a gearchange from the first gear stage 1 to the second gear stage 2, the shiftrail a performs the following motion in accordance with the diagramillustrated in FIG. 2. First of all, the first gear stage 1 isdeselected i.e. disengaged. The movement of the shift rail a starts attime t1 corresponding to a position −sg. The shift rail a now moves intoits neutral position, i.e. traverses the latter until time t0corresponding to a movement from −sg to +svs via −svs and “0” on thes-axis, at which time a presynchronization of the second gear stage 2begins. Only when the second gear stage 2 has been appropriatelysynchronized is the second gear stage 2 selected, i.e. engaged. Acorresponding shifting time ts between times t1 and t2 is obtained fromthe diagram illustrated in FIG. 2, and consequently the shifting timets=(t2−t1) corresponding to a movement from −sg to +sg on the s-axis.

[0050] The disadvantages of the prior art shift rail configuration areavoided by the shift rail principle according to the invention, which isillustrated in FIG. 3. The fundamental principle is that a plurality ofgear stages is assigned to at least two different shift rails in such away that respective successive ones of the gear stages are assigned todifferent shift rails. As a result, the respective shift rails can beactivated at least in part simultaneously in the case of a sequentialgear change. However, it is not necessary that all forward gear stagesthat follow one another sequentially are assigned to different shiftrails. It is, for example, also possible that only some gear stages,e.g. only the first four gear stages, are correspondingly assigned tothe different shift rails.

[0051] As can now be seen from FIG. 3, five shift rails a, b, c, d, ande are likewise provided here, as in FIG. 1. However, the gear stages 1to 8 and the gear stage R are assigned to the shift rails a, b, c, d,and e in a way different from the prior art. According to the invention,the first gear stage 1 and the third gear stage 3 are assigned to thefirst shift rail a, the second gear stage 2 and the fourth gear stage 4are assigned to the second shift rail b, and the fifth gear stage 5 andthe seventh gear stage 7 are assigned to the third shift rail c. Theillustrations in FIGS. 1 and 3 show a total of eight gear stages here.According to FIG. 3, the fourth shift rail d is assigned to the sixthgear stage 6 and to the eighth gear stage 8. In contrast to that, theconfiguration in accordance with FIG. 1 has the seventh gear stage 7 andthe eighth gear stage 8 assigned to the fourth shift rail d.

[0052] As FIG. 3 furthermore shows, the reverse gear R alone is assignedto the fifth shift rail e. As a result, at least a number of the forwardgear stages can in each case always be arranged on or assigned to thedifferent shift rails a to e, with the result that it is always possiblefor the respective different shift rails to be activated at leastpartially simultaneously in the case of a sequential gear change, inthis case from gear stage 1 to gear stage 2 or from gear stage 2 to gearstage 3 or also from gear stage 4 to gear stage 5 etc. This reduces theshifting times for gear changes by virtue of the fact that theindividual phases or stages of motion of the different shift rails canoverlap, thus shortening the total shifting time. As a result, the phasein which the tractive force is interrupted during the shift operation islikewise shortened. The reduced interruption of the tractive forceduring shifts improves the shifting comfort in the case of power shifts.It is noted that the simultaneous motion of the different shift rails isachieved on the basis of the individually activatable actuators assignedto the shift rails, that is to say that the shift rails are notactivated by a central gear shift shaft, as is customary in the priorart. It is therefore necessary to ensure mechanically and/orelectronically that when two different shift rails are in motion (e.g.shift rails a and b), it is not also possible for two gears to beselected, i.e. engaged, at the same time since, otherwise, thetransmission could be destroyed. A simultaneous synchronization phase ofboth gear stages should likewise be avoided since, in case of asimultaneous synchronization of both gear stages, there would beincreased wear on the synchronizing devices.

[0053]FIG. 4 now shows the shift sequence of the shift railconfiguration according to the invention shown in FIG. 3. During a shiftbetween two gear stages, i.e. a gear change with different shift rails,parts of the motion of the shift rails can be performed in parallel,i.e. at the same time. According to the diagram illustrated in FIG. 4, agear change from gear stage 1 to gear stage 2, for example, isillustrated here. During this process, the first gear stage 1 isdeselected first, i.e. the first shift rail a is moved in an appropriatemanner, the motion beginning at time t1 corresponding to a shift travel−sg on the s-axis. At a certain time, the second shift rail b is movedin parallel, i.e simultaneously with the shift rail a, to the start ofpresynchronization, the first shift rail a stopping at the neutralposition “0” on the s-axis. In parallel with this, the second gear stage2 is correspondingly synchronized, and the second gear stage 2 isselected at time t2new. The shifting time for this shift sequence, whichis implemented in accordance with the method according to the inventionwith the aid of the transmission according to the invention, now amountsto the period of time between times t2new and t1.

[0054] Compared with FIG. 2, it can therefore be stated that the newshifting time ts=(t2new−t1), where

[0055] (t2new−t1)<(t2−t1). A saving in shifting time of dt is thereforeobtained, as is illustrated in FIG. 4.

[0056] Fundamentally, the invention is therefore based on the principlethat shifting motions of different shift rails are made possible inparallel, i.e. can occur at the same time, for sequential gear changes.This is achieved, in particular, by changing the respective gearassignments, i.e. assignments of the gear stages to the individual shiftrails. In the configuration as illustrated in FIG. 3, all sequentialgear changes, i.e. the gear changes from R to the first gear stage 1,from the first gear stage 1 to the second gear stage 2, from the secondgear stage 2 to the third gear stage 3, from the third gear stage 3 tothe fourth gear stage 4 etc. can take place with the sequences of motionof the different shift rails a to e made in a parallel manner.Fundamentally, it is not possible for the motions of the individualshift rails a to e to be made in a parallel manner in the configurationillustrated in FIG. 3 if, for example, one gear stage is to be omitted,in other words one gear stage is to be skipped. In general, a parallelmotion for shift rails in the case when a gear is skipped, does not seemto be absolutely necessary since such a shift generally does not or atleast not always take place under full load and hence can also take upmore time, without having adverse effects for example on the shiftingcomfort. However, it is also possible to implement correspondingpartially simultaneous “motion components” of different shift rails forthe above-mentioned type of shifting which involves skipping acorresponding gear stage. This can be implemented by an appropriatechange in the gear stage assignment.

[0057] Finally, it is possible that shifts, i.e. gear changes, whichcannot take place in parallel, even with a modified gear assignment, canbe made quicker if the functionless region around the neutral positionis reduced. This has the effect that the distance traveled is shorterand is traversed correspondingly more quickly given the same speed. Atthe same time, however, care should be taken to ensure that there is asufficiently large range of motion remaining between thepresynchronization positions, which also ensures reliable deactivationof the corresponding gear stages.

We claim:
 1. A transmission for a motor vehicle, comprising: shiftrails; gear stages assigned to said shift rails; said shift rails beingconfigured such that, in a gear change, respective ones of said shiftrails are activated at least partially simultaneously; coupling unitsoperatively connected to respective ones of said shift rails andconfigured to select and deselect said gear stages for performing gearchanges; actuators operatively connected to respective ones of saidshift rails; and said coupling units being configured to be activatedvia respective ones of said shift rails and respective ones of saidactuators.
 2. The transmission according to claim 1, wherein: a firstone of said shift rails has a first and a third one of said gear stagesassigned thereto; and said first one of said shift rails is activated bya first one of said actuators.
 3. The transmission according to claim 2,wherein: a second one of said shift rails has a second and a fourth oneof said gear stages assigned thereto; and said second one of said shiftrails is activated by a second one of said actuators.
 4. Thetransmission according to claim 3, wherein: a third one of said shiftrails has a fifth one of said gear stages assigned thereto; and saidthird one of said shift rails is activated by a third one of saidactuators.
 5. The transmission according to claim 4, wherein: said thirdone of said shift rails further has a seventh one of said gear stagesassigned thereto; and a fourth one of said shift rails has a sixth andan eighth one of said gear stages assigned thereto.
 6. The transmissionaccording to claim 1, wherein said shift rails, said coupling units andsaid actuators form a motor vehicle transmission configuration.
 7. Thetransmission according to claim 1, wherein said shift rails, saidcoupling units and said actuators form an automated shift transmissionconfiguration.
 8. The transmission according to claim 1, wherein saidcoupling units are sliding collars configured to be engageable anddisengageable.
 9. The transmission according to claim 1, wherein saidgear stages are assigned to said shift rails such that respectivesuccessive ones of said gear stages are assigned to respective differentones of said shift rails.
 10. The transmission according to claim 1,wherein said shift rails are configured such that, when skipping atleast one gear in a gear change, respective ones of said shift rails areactivated at least partially simultaneously.
 11. The transmissionaccording to claim 1, wherein said shift rails are configured such that,in a sequential gear change, respective ones of said shift rails areactivated at least partially simultaneously.
 12. A method forcontrolling a transmission for a motor vehicle, the method whichcomprises: providing gear stages assigned to at least two shift rails;and performing gear changes by using coupling units activated viarespective shift rails and respective actuators for selecting anddeselecting the gear stages in the transmission and, in case ofperforming a gear change, activating respective ones of the shift railsat least partially simultaneously in order to perform the gear change.13. The method according to claim 12, which comprises: activating afirst shift rail by using a first actuator; and respectively selectingand deselecting a first gear stage and a third gear stage by using thefirst shift rail.
 14. The method according to claim 13, which comprises:activating a second shift rail by using a second actuator; andrespectively selecting and deselecting a second gear stage and a fourthgear stage by using the second shift rail.
 15. The method according toclaim 14, which comprises: activating a third shift rail by using athird actuator; and respectively selecting and deselecting a fifth gearstage and a seventh gear stage by using the third shift rail.
 16. Themethod according to claim 15, which comprises: activating a fourth shiftrail by using a fourth actuator; and respectively selecting anddeselecting a sixth gear stage and an eighth gear stage by using thefourth shift rail.
 17. The method according to claim 12, which comprisesproviding the coupling units as selectively engageable and disengageablesliding collars.
 18. The method according to claim 12, which comprisesproviding the gear stages assigned to the at least two shift rails suchthat respective successive ones of the gear stages are assigned torespective different ones of the shift rails.
 19. The method accordingto claim 12, which comprises activating respective ones of the shiftrails at least partially simultaneously in order to perform a sequentialgear change.
 20. The method according to claim 12, which comprisesactivating respective ones of the shift rails at least partiallysimultaneously when skipping at least one gear in a gear change.